First generation immigrants are still a tiny minority of the population. The fact that the entire team consists effectively of first generation immigrants says something, probably both about higher education and American culture.
For an American, it's less of a good deal. Once you have the PhD, you make somewhat more money, but you're trading that for 6 years of hard work and very low pay. The numbers aren't favorable -- you have to love the topic for it to make any sense.
As a result, U.S. PhD programs are heavily foreign born.
About 1/8 of the US population is foreign-born, which is a minority but not a tiny one. In California, its over a quarter.
The US population is around 330 million. The world population is 8.1 billion people. What is that 4%? If you took a random sampling of people around the world, none of them would be Americans. You're going to need a lot more samples to find a trend.
Yet when you turn around and look at success stories, a huge portion of this is going to occur in the US for multiple reasons, especially for the ability to attract intelligence from other parts of the globe and make it wealthy here.
There is a motivation that comes with both trying to make it and being cognizant of the relative opportunity that is absent in the second-generation and beyond.
There are also many advantages given to students outside the majority. When those advantages land not on the disadvantaged but on the advantaged-but-foreign, are they accomplishing their objectives? How bad would higher education have been in Europe? What is the objective, actually?
Not in California. Last I remember, something like a quarter of the state’s population is foreign born.
> All Students in Higher Education in California
> 2,737,000
> First-Generation Immigrant Students
> 387,000
14% are first-generation immigrants
from: https://www.higheredimmigrationportal.org/state/california/